My name is Jay and I've had a 12 gallon community tank for a couple of years, stocked with guppies and what were 2 cory cats.
Besides the community tanks, I have several betta tanks.Now, my sob story...
I had a guppy just die literally in front of my eyes in the span of an hour or so about three weeks ago. He went from fine to dead in a matter of minutes. I am religious about water changes and cleaning my tanks. Honestly, I know a lot more about bettas than corys. After the burial, the death led me to check the water and I did find nitrates a little high (I think old tank syndrome). So, I religiously continued to do water changes. I had been using a python and sucked up the gravel and water at the same time. (Now, I realize with corys that was probably very wrong.) I thought the guppy death at the time might have just been a fluke or a combination of stress brought on by high nitrates and preexisting disease (now I think differently, below).
The nitrates went down over the period of a week and then I lost a cory very quickly. Both corys went from scavenging to very lethargic and hiding constantly. They wouldn't eat. Then the one that died just stopped breathing. After his burial, I quarantined the other cory. After realizing that I probably stirred up a bacterial bloom with my python cleaning, I have been treating his quarantine tank with Melafix. He's been in there 5 days. He has good moments and bad, where he is swimming upside down - still. He hasn't eaten in a couple of weeks and isn't moving really at all. He continues to get skinner. My spouse says to put him out of his misery, which I won't do. He is truly a fighter with a will to live. He doesn't have any noticeable spots, abrasions, ulcers, etc. He just doesn't move and sometimes surfaces for air even though all my tanks are very well aerated.
Any help to save my last beloved cory would be greatly appreciated. Like I said, this one is a fighter and I don't want to give up on him.
Thanks for your help and happy to be here!